Comparing centralized defense and distributed defense

We've discussed the success of the passengers of United 93 at thwarting the 9/11 attacks before. I was reminded of it recently when I heard this quote from Ralph Raico's 2009 Mises University lecture "On War and Liberty" (at 27:09):

Some Defense Department! When 9/11 came, after having spent trillions of dollars, the Pentagon was not even able to defend its own headquarters from attack.